Refactor test/dune and add a failing test

The failing test shows how writes during a change_and_push are not
readable.

test/dune

@@ -1,14 +1,21 @@
+(env (_ (binaries (../app/mgit.exe as mgit))))
 (cram
  (package git-kv)
  (applies_to simple)
  (locks p9418)
- (deps %{exe:../app/mgit.exe}))
+ (deps %{bin:mgit}))
 
 (cram
  (package git-kv)
  (applies_to fold)
  (locks p9418)
- (deps %{exe:../app/mgit.exe}))
+ (deps %{bin:mgit}))
+
+(cram
+ (package git-kv)
+ (applies_to fold2)
+ (locks p9418)
+ (deps %{bin:mgit}))
 
 (executable
  (name git_daemon_exists)

test/fold2.t

@@ -0,0 +1,16 @@
+Reading during batch operation
+  $ mkdir simple
+  $ git init --bare -q simple 2> /dev/null
+  $ git daemon --base-path=. --export-all --enable=receive-pack --reuseaddr --pid-file=pid --detach
+  $ mgit git://localhost/simple#main << EOF
+  > fold
+  > set /bar "Git rocks!"
+  > get /bar
+  > quit
+  > quit
+  00000000: 4769 7420 726f 636b 7321                 Git rocks!
+  $ cd simple
+  $ git log main --pretty=oneline | wc -l
+  1
+  $ cd ..
+  $ kill $(cat pid)